This application relates to frequency selective networks for microwave circuits, particularly those employing dielectric resonators.
Frequency selective networks for microwave circuits have been constructed employing as a resonator a piece of material having a relatively high dielectric constant, the resonator being coupled to associated circuitry by a pair of input and output coupling loops. The shape of the resonator is typically a disc, one coupling loop being disposed adjacent one flat side of the disc, and the other coupling loop being disposed adjacent the opposite flat side of the disc. In the absence of the disc, the two loops would be decoupled by virtue of the spacing between them; however, they are coupled to one another through the disc. In such a network, which may be used as the frequency sensitive portion of an oscillator or as a band pass filter, the piece of dielectric material functions like a cavity resonator.
Such networks are desirable in many applications because, due to the high dielectric constant of the dielectric resonator, they can be constructed with small physical dimensions relative to their resonant frequency, and because they provide a high Q (quality factor) device. However, conventional construction of such a device requires that the coupling loops, which are typically conductors formed in a circuit board, be placed in separate circuit boards located on opposite sides of the resonator. This introduces undesirable physical separation of electronic components and undesirable mechanical packaging requirements for associated microwave circuitry.
It would be desirable to construct such a network whereby the coupling loops are formed in a single circuit board, thereby simplifying both the electrical and physical design for the associated circuitry.